[Morphological data correlated with the mechanism of striated muscle contraction]

The classical theory of muscle contraction (Huxley, 1957) could not entirely explain a series of theoretical and experimental data. This theory sustains a longitudinal sliding of thin filaments on thick ones, by the tilting of myosin cross-bridges. Under different stimuli inducing contractions, the stereospecific conformations of cross-bridges appear to be different as it is shown using electron microscopy, fluorescence polarization, electron paramagnetic resonance (EPR) spectroscopy and equatorial X-ray diffraction. Our optic microscopy data also suggest the existence of such conformations, induced by different contractile stimuli.